Inflatable restraint systems are now commonly utilized in motor vehicles as passive occupant restraint devices for impact protection. The air bag of an inflatable restraint system inflates during a collision in response to an electrical signal generated from one or more crash sensors mounted to the motor vehicle. The inflated air bag provides energy absorption and an improved contact surface for motor vehicle occupants in the event of a crash.
Side impact air bag systems have been developed which deploy during side impact collisions. Generally, side impact air bags are housed in the vehicle seat or in an inner surface of the vehicle door. Air bags housed in the vehicle seat are typically deployed through a tear seam in the seat cover material.
The timing of a side impact air bag system is very critical to the success of the cushioning device. For a typical side impact, the air bag system must sense the crash and deploy the air bag within 10-15 ms. Therefore, any delay in the deployment of the air bag could cause a decrease in the amount of protection given by the air bag device.
A conventional vehicle seat having a seat deployed side impact air bag has a sewn tear seam located on the seat cover. In order for the air bag to properly deploy, the seat cover seam should separate in a predictable manner. However, a sewn tear seam can act unpredictably during air bag deployment. Such factors as the type of material used on the seat cover, the type of thread used to sew the seam and the type of stitch used all add to the unpredictability of the sewn tear seam. Therefore, it is possible that air bag deployment may be delayed or even prevented during a side impact crash due to the unpredictability of the sewn seam.
Another disadvantage of using a sewn tear seam is that it is not reusable. When the air bag is deployed, the seat cover is damaged and either the seat or seat cover must be replaced or the seam must be resewn. This results in a high average repair cost (ARC) which generally leads to higher insurance premiums. Furthermore, if the tear seam is resewn, the unpredictability of the tearing characteristics of the repaired seam increases.
Servicing the air bag module also presents a problem. Because servicing the air bag module generally results in damage to the seat cover and seam, the seam must be resown. This presents problems similar to those mentioned above.
Vehicle seats having a sewn tear seam also present manufacturing problems for the vehicle manufacturer. The vehicle manufacturer is required to use vehicle seats which have been previously assembled to include the seat deployed air bag modules or sew over the tear seam on the assembly line after the air bag module has been installed in the seat. This results in higher manufacturing costs and increased assembly time.
Thus, there is a need for a vehicle seat tear seam for seat deployed side impact air bags which acts in a predicable manner during air bag deployment. There is also a need for a vehicle seat tear seam which can be resealed after an air bag deployment thus lowering the average repair cost. There is a further need for a resealable vehicle seat tear seam which would facilitate easy service and maintenance of a seat deployed air bag module contained within the vehicle seat without damaging the vehicle seat cover. There is a still further need for a vehicle seat tear seam which would allow vehicle manufacturers to easily install air bag modules into vehicle seats during vehicle manufacturing.